The present invention relates generally to systems for traffic monitoring and management. More particularly, it relates to apparatus and method for utilizing a two-way radio transponder to accurately and automatically determine the lane position of vehicles as they traverse a roadway, bridge, tunnel or other form of transport such as a railway.
An increasing number of vehicles are traveling over progressively more congested transportation networks. In order to improve the efficiency of transportation networks, automated travel management systems are being employed to optimize the capabilities of these networks. One example of particularly severe inefficiency and congestion is toll plazas, where, under present circumstances, traffic must be completely halted in order to safely perform the manual exchange of currency for the right to proceed. The collection of tolls by conventional means has had a negative effect upon highway throughput and safety. Congestion and long backups at toll plazas are becoming more common, the resulting delay, expense and reduced productivity are becoming more burdensome.
In response to the inability of conventional toll collection means to meet the demands created by increased highway traffic, automated toll facilities that provide improved toll collection methods and systems have been proposed. These automated toll facilities eliminate the manual transactions of conventional toll collection means through the use of radio transmitters and receivers that perform the necessary transactions as a vehicle travels through the automated toll booth. One such system electronically collects tolls from an electronic cache of toll credits carried within the vehicle. In this way, a vehicle operator can purchase a quantity of toll credits prior to traveling on a toll road. As the vehicle later travels through a toll collection booth, a radio-frequency exchange occurs and the appropriate amount is automatically debited from the vehicle's toll credits.
Although the automated toll collection system described above functions well for single lane toll roads or single lane bridges and tunnels, a significant problem can exist when the system is practiced in a multi-lane environment. In a multi-lane environment, each toll lane is equipped with a stationary radio-transceiver to interact with the mobile radio-transceiver of vehicles passing through that lane. The problem of multi-pathing occurs when information transmitted from a vehicle in one lane is picked up by multiple toll lane stationary transceivers. Therefore the possibility exists that a toll collected from a vehicle in lane 1 may be credited to the vehicle in lane 2. The effect of multi-pathing allows toll-evaders to exploit automated toll systems, as well as accidentally misallocating the debits.
A number of prior art systems exist that minimize the effects of multi-pathing. These systems typically attempt to shield the toll transceiver of one lane from signals transmitted from mobile units traveling in an adjacent lane. Such systems include methods that establish a proximity zone that identifies when a vehicle has entered a predetermined region, and then requires the vehicle to transmit the toll within a predetermined time limit. Other systems establish a multi-field environment, where a blanking field is transmitted behind and adjacent to a region proximate to the toll lane. The blanking zone serves to swamp out any multi-path signals that could be received by the toll station. The prior art systems do not provide a means for determining the actual lane position of an oncoming mobile unit. Because of this, the prior art systems do not allow the toll system to determine the physical sequence of oncoming traffic approaching the toll system. Moreover, the prior art systems place constraints on the size of the lanes and the spacing that must exist between each lane transceiver.
Accordingly, an object of the present invention is to provide a system for determining the lane position of a vehicle approaching an automated toll system.
A further object of the invention is to provide a mechanism for determining the sequence of mobile units approaching an automated toll system.
An additional object of the invention is to provide a system for determining the relative position of a mobile object approaching a stationary transceiver.
And yet another object of the invention is to provide a system for automatic toll collection that uses toll transceivers that can work in close proximity with other toll transceivers.
Other general and specific objects of the invention will in part be obvious and will in part appear hereinafter.